Research objectives of this study are to evaluate the effect of increasing or decreasing atrial receptor activity on plasma ADH concentration and renal function in the conscious dog. The effect of the experimental maneuvers on atrial receptors will be documented by recording atrial receptor discharge from afferent impulses in the cervical vagus nerves in anesthetized dogs. We also propose to do a series of localizing experiments in an effort to confirm whether the effect of certain cardiopulmonary receptors on ADH secretion and renal function differs from that of others in nearby regions.